As we are currently working on our site, one suggestion/idea.
The situation is the following:
A portal where a customer logs in using SSL. Consecutive Pages are entirely delivered via SSL.
Most pages consist of a dynamic, customer specific base page, with an additional 50+ static objects. As you do not want to challenge your customer with a "There are secure and unsecure objects"-message, asking to cancel or proceed, all these static objects are delivered via SSL as well.
Now Firefox normally puts these objects only in the very, very small Memory Cache, which flushes after closing the Browser.

To achieve caching these objects Firefox uses the cache-control: public directive.
How about a performance/optimization criteria, that recommends for cacheable objects over SLL using this directive, to allow disk-caching in Firefox?